1. Field of the Invention
The present invention relates generally to an apparatus for laying and lifting large precast concrete pipes for use in sewers and water mains. More specifically, the invention is a lockable and releasable scissors grip apparatus for laying large pipes.
2. Description of the Related Art
In the construction industry, it becomes necessary to lift and move large segments of pipe which are often precast concrete and weigh many tons. Some of the requirements that exist with respect to such pipe handling by lifting apparatus for moving heavy metal or concrete pipes include: stability, strength, resistance to torsion forces, rotational versatility, and safe ergonomic handling by workers. A number of different jaw or tong-type apparatus designed for suspension from a crane have been employed to fulfill these requirements, but such relevant art apparatus has had limited success in at least one or more respects. Each apparatus utilizes the common principle of the construction tong, i.e., the clamping force upon the pipe increases with its weight. The relevant art of interest will be described in the order of perceived relevance to the present invention.
U.S. Pat. No. 3,008,753 issued on Nov. 14, 1961, to Geno Tazioli describes a pair of pipe tongs with their pivot points connected by a single stabilizer. The tong handles are connected by a pair of pivot link bars to the ends of a hollow horizontal frame which houses the release mechanism for the tongs by attaching a spring to each pivot point. A cable is attached to each spring and attached to a ratchet and ratchet lock device with a release mechanism located in the center of the hollow housing. The release mechanism of this device is distinguishable for its different structure involving cables and springs.
U.S. Pat. No. 1,877,974 issued on Sep. 20, 1932, to John F. Robb describes a pipe line depositing machine operated with an endless track tractor having an extension from the side of a track to attach by a shoe to the pipe. The boom supports a pair of roller connected tongs (FIG. 6) or a single tongs (FIG. 1) by link members to a hook with a cable extending from the tongs to shoe. The tongs are released by a lever (at the pivot point) and cable attached to the tractor. The apparatus is distinguishable for its required connections to a tractor and the cabled release mechanism.
U.S. Pat. No. 3,897,969 issued on Aug. 5, 1975, to Clarence L. Dike describes a grapple for hoisting pipes. In FIG. 6, a pipe is carried by a spreader I-beam from which hang two grapples from chains. The flat grapple arms have an extension consisting of an upstanding flange and a perpendicular horizontal flange having a cushion. Each grapple has a leverage device and a safety device. The safety device has a wire rope attached to the outsides of the two upstanding flanges and linked by another wire rope to the grapple chains. If the chain breaks, the wire ropes will still hold the pipe. The leverage device is utilized to open the jaws and has an opening cable. The grapple system is distinguishable for its multiple cable (wire rope) usage for keeping the jaws open or closed.
France Patent Application No. 1,185,260 published on Jul. 31, 1959, for M. Marcel Tranchard describes a tongs with arcuate flanges on the inside surfaces of the jaws. A movable hook appears on one of the uppermost arms apparently for locking onto a pin on a lower arm of the tongs. The tongs with the locking mechanism is distinguishable for its purpose which apparently is to keep the jaws open and lacks any mechanism for its release.
U.S. Pat. No. 5,364,147 issued on Nov. 15, 1994, to Thomas E. Dickey et al. describes a device for handling a plurality of railroad timbers having a square cross-section. In FIG. 9, two pairs of inner actuating levers are held by chains to a hoisting hook. The levers are held together by a system of crossbars. Each lever has its bottom end bolted to the outside railroad tie. Two steel strapping members hold the ties together. The device is distinguishable for its fixed position of the jaws.
Switzerland Patent Application No. 354,564 published on Jul. 15, 1961, for Sergio Verdini describes a scissors clamp having crossbars at the ends of each jaw and an adjustable crossbar between the two arms of the jaws. The apparatus is distinguishable for its fixed jaws relationship.
U.S. Pat. No. 4,030,625 issued on Jun. 21, 1977, to Edward L. Koehnen describes a loader attachment for a tractor for handling logs, bales and the like. A scissors acting pair of hooks are connected by a horizontal pivot bar. The upper arms of the hooks are connected by links to a lifting strap which rides on hook control crank arm from a pulley. The crank arm is controlled by a control rod attached to a lever on the tractor. The apparatus is distinguishable for its weak structure.
U.S. Pat. No. 5,666,758 issued on Sep. 16, 1997, to George L. Vaillier et al. describes a retrieval mechanism for retrieving small articles comprising a scissors mechanism with cross members at the ends of the jaws perpendicular to the jaws and having a plurality of teeth facing inward. The links to the jaws are connected to a plate having two wire loops for containing a fishing line while retrieving a lure. The retrieval mechanism device is distinguishable for its limited use.
U.S. Pat. No. 5,056,845 issued on Oct. 15, 1991, to Carol A. Cook describes a concrete highway divider lifting apparatus with scissors actuated jaws having extended flattened surfaces of various types. An adjustable crossbar between the upper arms of the jaws maintains a fixed grip on the carried object. The apparatus is distinguishable for its fixed jaws.
However, it should be noted that other than having the common trait of utilizing the tong principle, the relevant art does not have the elements necessary to fulfill the requirements or the capabilities of the present inventive lifting apparatus.
None of the above inventions and patents, taken either singularly or in combination, is seen to describe the instant invention as claimed. Thus, a precast concrete pipe lifter apparatus solving the aforementioned problems is desired.